Time delay relay



NOV. 1, 1938. E ET AL 2,134,951

TIME DELAY RELAY Filed March 29, 1935 INVENTORS BRUNO PIES/FER W Go Y (lQim ATTORNEY.

Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE TIME DELAY RELAY Bruno Piesker and Wilhelm Goy, Frankfort-nthe-Main, Germany,

assignors to Prazisions- Werkstatten Seeger & 00. G. m. b. 11., Frankfort-on-the-Main, Germany, a corporation of Germany Application March 29,

1935, Serial No. 13,684

In Germany January 6, 1934 Claims.

I'erred to in the art as time delay relays and.

obtained the time delay elfect by one of the three following means:

1. By heating a metallic and deformable conductor, for example a wire or strip of metal by the action of an electric currentand using the heat expansion for actuating an electrical contact.

2. By connecting condensers or resistances across the relay winding.

3. By arranging short circuit windings or copper tubes around the relay winding.

None of these means Was satisfactory or successful in providing a completely practical and reliable time delay relay. The heating devices had the disadvantage of taking aconsiderable time after the completion of the electrical con nection before they started to operate at all because they had to be heated up to a definite high operating temperature. In addition, the time delay between the connection of the operating current and that of the controlled current varied considerably with variations of the temperature of the surroundings and of the linevoltage. These devices have been especially unsatisfactory when they have been used in self-interrupter circuits where it was important to have constant time intervals between successive contact interruptions.

The second and third systems have been partly successful in delaying the release of the relay armature by up to ol a second after interrupting the actuating current. However, it was not possible to increase the time delay beyond this limit. In addition, relays of this type have been rather unreliable and after a relatively short operation the armature frequently stuck to the stop screws, pins or surfaces used to limit movement of the armature. This was known to be due to the oxidation and corrosion of the stop pins or surfaces under the influence of the atmospheric oxygen. Due to the so-called sticking of relays, the stops or intermediate layers,- usually made of copper, interposed between the armature and the pole shoe determined the air gap and could not be reduced below a certain value because theseold protective layers of copper or the like were used up so quickly that the relays stuck after a relatively short operating time, On the other hand, if the air gap was increased by providing a thicker intermediate layer of copper or extending the length of the stop pin, this increased the distance between the pole shoe and the armature and thereby sped up the release of the armature. Accordingly, it is clear that the art'has been confronted with the serious problem of reconciling these two opposite requirements, but, as far as we are aware, none of the many suggestions and proposals has been completely satisfactory or successful.

We have discovered that the problem can b solved in a remarkably simple manner.

It is an object of the present invention to provide a. simple and efficient time delay relay which is capable of obtaining very considerable time diiierences or delays between actuating the magnetizing current and the actuation, pick up or release of the relay armature.

It is another object of the present invention to provide a time delay relay capable of very much delayed operation which is free from the vexatious elTe'cts of oxidizing, oxide deposits and in uhich the armature cannot be obstructed in its easy and free movement or cannot stick.

It is a further object of the invention to provide a simple and inexpensive time delay relay of small dimensions and of low current consumption which can be advantageously used in a selfinterrupter circuit for Opening and closing the circuit of electric lamps at predetermined intervals.

' The invention also contemplates a time delay relay which is adapted to be used to produce flashing light and danger signals.

Other and further objects and advantages of the invention will appear from the present specification taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a front elevational view, partly in section, of a time delay relay embodying our inven-' tion, with the copper tube covering the relay winding partly broken away for the purposes of clarity;

Fig. 2 depicts a side elevational view of Fig; 1;

Fig. 3 illustrates a side elevational view of the yoke of the relay shown in Fig. 1;

Fig. 4 illustrates a modified form of yoke used in connection with our improved time delay relay; and

, Fig. 5 shows a somewhat fragmentary view of another embodiment of the present invention.

We have discovered that the time delay effect and the reliability of the relay can be increased by providing at the points where the armature is striking against the pole piece or the yoke an intermediate layer of very small thickness said layer consisting of a non-magnetic, non-oxidizable or at least difiicultly oxidizable solid material. This layer is preferably provided in the form of a coating or plating either on the armature or on the pole shoe or yoke or on all of them. It is also possible to provide the intermediate layer in the form of a separate and independent strip or plate of metal or other suitable material and arranged in between the armature and the pole shoe. In this case, however, it is important that oxidation of the surface of the armature, pole shoe and yoke generally made of iron should be also prevented.

We are aware that intermediate layers of a non-magnetic material, as, for example, copper, have been already known in the art, but these layers have been oxidizable or corrosive or have contained oxides of these metals which have been formed either during the actual operation of the relay or artificially, for example, by heat treatments. It has also been suggested to use certain liquids, for example, oil to provide an intermediate layer, but such materials cannot be very well used for producing a time delay effect because the effect of the purely physical adhesion is too great and would considerably increase the current needed for operating the relay. Preferable non-magnetic and non-oxidizing substances for providing an intermediate layer according to the principles of the present invention are the following:

Pure aluminum or its alloys, gold, silver, tin, cadmium, non-magnetic alloys of nickel, or of other non-corroding metals. We have found that non-metallic substances, asfor example, lacquers, artificial resins and other insulating materials can be used with advantage provided they have the sufficient mechanical strength to resist the vibrations or shocks during the strike of the armature against the pole. Of these materials, aluminum is covered by an extremely fine layer or film of its oxide which, however, in contrast to the oxides of iron and copper adheres very firmly to the metal. In addition, the oxide of aluminum is completely non-magnetic and provides a satisfactory non-magnetic intermediate layer. As a matter of fact, it is frequently advisable to provide on purpose a hard and resisting oxide layer on the aluminum, for example, by means of an anodic treatment because oxide layers obtained in this manner provide very durable, non-magnetic and non-oxidizing intermediate layers which are very advantageous for the purpose of the present invention.

In addition to the intermediate layer, we found that it is of advantage to make the armature, the pole shoe and the yoke partly or completely of suitable magnetizable metals having a very high degree of chemical purity so that the formation of oxides under or through the non-magnetic intermediate layer is prevented. This can be realized, for example, by making armature, pole shoe,

"and yoke completely or only on the surface of a non-rusting iron-nickel-chromium alloy or of iron which has been nickel or chromium plated. In this manner, the non-magnetic intermediate layer will have an especially long useful life.

The non-magnetic and non-oxidizing intermediate layer may be made of microscopical thickness i. e. 0.04 mm. or of any other preferred thickness. It may be provided, for example, by electroplating, it may comprise a plurality of individual layers provided one on top of the other or separated from each other by other layers. Of course, the magnetic forces acting on the armature will be diiferent for different arrangements of the intermediate layers so that in this manner, within certain limits, any desired time delay of the armature release can be obtained. In contrast to the prior relays having stop screws or pins for adjusting the movement of the armature, the relay according to the principles of the present invention has absolutely no air gap in the magnetic circuit when the armature is picked up and only the non-magnetic and non-oxidizing intermediate layer provides a non-magnetic gap. Of course, this thin, skin-like intermediate layer cannot be affected by the atmospheric oxygen and the air tight contact of the armature with the pole shoe prevents direct contact of the oxygen with the places where the armature is striking.

We have found that the relay embodying our invention is capable of further refinements which are especially important when the relay is used as a self-interrupter or for short-circuiting itself in order to provide automatic opening and closing of contacts at predetermined time intervals. Circuits of this type are especially in use for controlling the circuit of signal lamps in order to provide flashing light and danger signals. To obtain the necessary slow operationfit is of importance that not only the release but also the pick up of the armature should be considerably delayed. The greatest time delay in the pick up obtainable heretofore with telephone relays provided with a copper cylinder and short circuit winding is approximately of a second. Of course, this time delay is insuificicnt for a relay providing a flashing light effect. We have found, however, that the principles of the present invention can bearplied to delaying the pick up of the relay armature, and, more particularly, have found that a relay of especially slow operation can be provided by applying the non-magnetic and non-oxidizing intermediate layer on a relay having its armature bent at an angle. A relay of this type and embodying the principles of the present invention is shown in Fig. 1 of the drawing.

Referring now more particularly in Fig. 1, a yoke I made of a magnetizable material has secured thereto a magnetizable core 2. This core is provided with a winding 3 and a pole shoe 4. An armature 5 made of a flat piece of a magnetizable material and bent at an angle is pivoted or balanced on an edge at 6. Two contact springs 10 and H having contact points l0 and II are held by a dielectric l3 and maintain an electrical circuit closed in the normal position of rest of the armature, shown in Fig. 1. When the relay winding proper 3 is energized, one end of the armature will be picked up by the pole shoe 4, the other horizontal end of the armature by means of pin I 2 made of an insulating material will push contact spring 10 upwards and will break the circuit between 10' and II. All surfaces of the armature, yoke and pole shoe which strike against each other in operation are provided with a very thin intermediate layer 9, 9' and 9" of a non-magnetic, non-oxidizing material. Of course, in practical operation, it is the simplest to provide not only these but also all other surfaces of these co-operating parts with a thin coating or plating of said non-magnetic and non-oxidizing material. It is noted that in contrast to conventional relays, the present relay is not provided with stop screws, pins and the like to limit the movement of the armature, but the armature when picked up will rest with its full surface on the pole shoe and is separated therefrom only by the thin intermediate layer but by no air gap.

We have found that if it is desired to produce flashing light signals or danger signals by our time delay relay, it is to be preferred to connect the electric lamp in parallel or across the relay winding and not in series therewith as this was customary in prior devices. A circuit of this type is shown in Fig. 1 in which an electric lamp I5 is connected across the relay winding 3 which is connected in series with the contact points I0 and II and a source of current [9.

The operation of the relay is the following: When the circuit of winding 3 is completed, the winding will be energized and will pick up the vertical part of the armature 5. This will move the horizontal part of the armature upwards so that contact springs I0 and II will be separated and will break the circuit of the winding between contact points [0' and H. Hereafter the play of the armature begins anew and will be maintained so long as current is supplied to the relay.

Each time the circuit is interrupted, an induc-.

tion current impulse will be set up in the winding 3 and will light up lamp l5 for a short time with great intensity. We have found that the light impulses produced in this manner are very clearly defined and are easily noticed from a considerable distance so that they have great advantages over prior danger signals.

In most cases, we prefer to provide longitudinal or transversal slots, cuts or incisions on the yoke as shown by the reference character IS in Figs. 3 and 4. These incisions or gaps increase the magnetic stray field of the relay acting on the horizontal part of the armature and prevent quick separation of the armature from the yoke. The increase of the magnetic stray field by means of the incisions on the yoke has the additional effect of delaying the pick up quite considerably.

A further means of increasing the time delay of picking up the armature is to provide under or in front of the pole shoe 4 of the relay shown in Fig. 1, a U-shaped brake member 8 made of iron or steel sheet of suitable thickness and preferably attached to pole shoe 4 by means of an extension. As will be observed from Fig. 2, this sheet is so bent that its two sides are either in direct contact with the side of the armature or they are separated therefrom by a very small air gap. When the relay winding is energized, and the armature is attracted by the pole shoe, the relatively strong magnetic field between the sides of the U-shaped member, through which the armature has to move, will slow down the pick up of the armature. Preferably, the U-shaped brake member is made of a very thin sheet of magnetizable metal so that the sides thereof will be attracted by the stray field of the armature and will be brought into direct contact with the armature. Thus, the armature on its way toward pole shoe 4 will slide on the two sides of the U-shaped member and the friction produced will further slow down the pick-up of the armature.

Fig. 5 illustrates a further embodiment of our invention, which in its operation is much similar to the arrangement of the U-shaped member described hereinbefore. In this embodiment a small magnetizable part I"! is pivoted at the end of the horizontal part of the armature 48. When the winding of the relay is energized and the armature is attracted, the little part I! will slide along the surface of the yoke I and thereby will increase the time delay of the pick up. In the embodiment shown in Fig. 5, the non-magnetic and non-oxidizing intermediate layer is provided in the form of a separate strip 9 of metal or other suitable material. Preferably, the edge of the yoke I where the armature 5 is balanced is provided with a suitable groove or depression 2| in which the strip 9 is embedded. This is desirable otherwise the armature would chafe through the thin intermediate layer where the same is located on the sharp edge of the yoke and would considerably shorten its useful life.

A movable intermediate layer similar to strip No. 9 may also be provided when a thin film of firm, non-magnetic and non-oxidizing material is present on the surfaces of the pole-shoe, yoke or armature. This movable intermediate layer serves in these circumstances to further improve the durability of the thin. film. It is probable that this intermediate layer in some way or other weakens the impact of the armature against the pole-shoe. If the thin layer is made of a nonmagnetic material the movable intermediate layer may consist of a magnetic or a non-magnetic material. If it consists of non-magnetic material it has a magnetic effect in addition to the intermediate layer on the armature and poleshoe. The movable intermediate layer may also be composed of magnetic material such as nickel and chrome-containing iron alloys. In this case the film of non-magnetic material prevents any undesired sticking of the armature and the magnetic movable layer improves the latters durability.

If the .armature is bent to an angle a suitable groove or depression is provided in which the movable layer is embedded in order to prevent chafing of the intermediate layer by the movement of the armature.

To protect the winding against injury, it is advisable to coverthe same with a metallic tube I4 which snugly fits over the winding. This metallic tube will afford the necessary protection and has the added advantage of further increasing the time delay of the operation" of the relay in consequence of the induction currents set up therein.

The applications of the time delay relay embodying the principles of our invention are many. The relay can be used, for example, in telephone and signalling equipments where it is necessary to have a great delay between the energizing of the winding and the pick up or the release of the armature. It is of especial advantage when slow current impulses are to be produced at predetermined time intervals, for example, for actuating signalling lamps or to produce flashing light and danger signals. An important application of the relay is to produce flashing light signals on motor vehicles to indicate the drivers intention to stop or to make a turn.

Although we have described our present invention in connection with a few preferred and practical embodiments thereof, many variations and modifications are possible and will suggest themselves to those skilled in the art without departing from the principles of the present invention. Especially the details of the invention may be applied whereby in combination with the relay illustrated in the designs, in which the armature is bent at an angle but also in combination with all other known types of relays. We consider all of these variations'and modifications as within the true spirit and scope of our invention as described in the present specification and defined by the appended claims.

We claim:

I. In an electromagnetic relay of delayed operation, the combination comprising a magnetizable core, a winding on said core, a movable armature for said core, a thin intermediate layer of a solid, non-magnetic and non-oxidizing material located between the cooperating surfaces of said core and said armature, and a deformable plate of magnetizable material located in proximity of said armature, said plate capable of being attracted and deformed under the magnetic action of said armature when said winding is energized whereby a surface of said armature will be frictionally engaged by said deformed plate and movement of said armature Will be delayed.

2. In an electromagnetic relay of delayed operation, the combination comprising a magnetizable core, a winding on said core, a movable armature of substantially oblong cross section for said core, a thin intermediate layer of a nonmagnetic and non-oxidizing material located between the co-operating surfaces of said core and said armature, and a deformable plate constituted of a magnetizable material located in proximity of said armature, said plate capable of being attracted and deformed under the 'magnetic action of said armature when said winding is energized whereby the side surfaces of said armature will be slideably engaged by said deformed plate and movement of said armature will be delayed by combinedmagnetic and frictional action of said plate.

3. In an electromagnetic relay of delayed operation, the combination comprising a magnetizable core, a yoke attached to one end of said core, a pole shoe mounted on the other end of said core, a winding aroundsaid core, a U-shaped resilient plate constituted of a magnetizable material located in proximity of said pole shoe, and a pivoted armature bent at an angle having one of its ends between the sides of said U-shaped plate, the sides of said plate capable of being attracted and deformed under the magnetic action of said armature when said winding is energized to slideably engage the side surfaces of said armature and to delay movement thereof.

4. In an electromagnetic rel'ay of delayed operation, the combination comprising a magnetizable core, a yoke attached to one end of said core, a pole shoe mounted on the other end of said core, a winding around said core, a pivoted armature bent at an angle adapted to complete the magnetic circuit of said relay, an intermediate layer of a solid, non-magnetic and non-oxidizing l'l'itilial between said armature said yoke and said pole shoe, and a U-shaped resilient plate constituted of a magnetizable material having its sides in proximity of the side surfaces of said armature, the sides of said plate capable of being attracted and deformed under the magnetic action of said armature when said winding is energized to slideably engage theside surfaces of said armature and to delay movement thereof.

5. In a time delay relay, the combination comprising a magnetizable core, a- Winding around said core, a yoke attached to one end of said core, a pole shoe mounted on the other end of said core, an armature bent at an angle pivoted on an edge at the end of said yoke, and a thin, movable and flexible strip of a non-magnetic and non-oxidizing material interposed between and independent from the co-operating surfaces of said armature, said yoke and said pole shoe, said armature capable of being picked up when said winding is energized and of being separated from said core solely by the thickness of said movable and independent strip providing a magnetic gap of greatly reduced length whereby pick up and release of said armature are delayed and sticking of said armature is prevented.

6. In a time delay relay, the combination comprising a magnetizable core, a winding around said core, a yoke attached to one end of said core, a pole shoe mounted on the other end of said core, an armature bent at an angle pivoted on an edge at the end of said yoke, a thin, movable and flexible strip of a non-magnetic and non-oxidizing material interposed between and independent from the co-operating surfaces of said armature, said yoke and said pole shoe, and a groove provided at the edge of said yoke where said armature is pivoted to receive and to hold said strip to prevent chafing thereof by said armature, said armature capable of being picked up when said winding is energized and of being separated from said pole shoe solely by the thickness of said movable and independent strip whereby pick up and release of said armature are a delayed and sticking of the armature is prevented.

'7. In a time delay relay, the combination comprising a magnetizable core, a winding around said core, a yoke attached to one end of. said core, a pole shoe mounted on the other end of said core, an armature bent at an angle pivoted on an edge at the end of said yoke, a layer of a solid nonmagnetic and non-oxidizing material provided on the co-operating surfaces of said pole shoe, said yoke and said armature, and a thin, movable and flexible strip of a non-magnetic and nonoxidizing material interposed between and independent from said co-operating surfaces, said armature capable of being picked up when said winding is energized and of being separated from said pole shoe solely by the combined thicknesses of said layer and said movable and independent strip whereby pick up and release of said armature are delayed and sticking of the armature is prevented.

8. In a time delay relay, the combination comprising a magnetizable core, a winding around said core, a yoke attached to one end of said core, a pole shoe mounted on the other end of said core, an armature bent at an angle pivoted on an edge at the end of said yoke, a layer of a solid non-magnetic and non-oxidizing material provided on the co-operating surfaces of said pole shoe, said yoke and said armature, and a thin, movable and flexible strip of a magnetic and non-oxidizing material interposed between and independent from said co-operating surfaces, said armature capable of being picked up when said winding is energized and of being separated from said pole shoe solely by the combined thicknesses of said layer and said movable and independent strip whereby pick up and release of said armature are delayed and sticking of the armature is prevented.

9. In a time delay relay, the combination comprising a magnetizable core, a winding around said core, a yoke attached to one end of said core, a pole shoc mounted on the other end of said core, an armature bent at an angle pivoted on an edge at the end of said yoke, a layer of solid non-magnetic and non-oxidizing material constituted of a lacquer provided on the cooperating surfaces of said pole shoe, said yoke and said armature, and a thin, movable and flexible strip of a magnetic and non-oxidizing material interposed between and independent from said co-operating surfaces, said armature capable of being picked up when said winding is energized and of being separated from said pole shoe solely by the combined thicknesses of said layer and said movable and independent strip whereby pick up and release of said armature are delayed and sticking of the armature is prevented.

10. In an electromagnetic relay of delayed operation, the combination comprising a magnetizable core, a winding around said core, a yoke attached to one end of said core, a pole shoe mounted on the other end of said core, a pivoted armature carrying no current bent at an angle and capable of substantially completing the magnetic circuit, and a thin intermediate layer constituted of solid, non-magnetic and non-oxidizing materials including lacquers and artificial resins located between the co-operatlng surfaces of said pole shoe, said yoke and said armature, said armature capable of being picked up by and of striking directly against said core when said winding is energized and of being separated therefrom solely by the thickness of said intermediate layer of lacquer providing a magnetic gap of greatly reduced length whereby pick up and release of said armature are delayed and sticking of the armature is prevented.

BRUNO PIESKER. WILHELM GOY. 

